Took our 11 month old on a return from DUB to MCO. On the way out, we had the bassinette seat, but she only slept for one hour out of nine! However, the rest of the time she either sat or stood in the crib, or stood on our knees...she loved the experience, seeing so many new faces, and watching all that was going on. Bring plenty of (new) toys, as these will hold attention for a while.
On the way back we had to negotiate with other passengers for a bassinette seat, even though we had been told by the gate staff that we were seated at one. Not good. Junior cried until we got her into bed, then slept like a baby (funny that) the whole way home.
As mentioned above, it's important for you to be chilled. If baby sees that you are relaxed, there's more chance that she will be too.